This investigation is a three year effort to develop a unique binary gas full-wave model that will simulate a multi-constituent gas and incorporate all relevant physical processes such as the Coriolis force, mean winds, eddy and molecular diffusion of heat and momentum, and reflection. This detailed treatment is necessary since the thermosphere is a diffusively separated multi-constituent gas in which individual species are in static equilibrium and are stratified according to their individual scale heights. The model will be the first realistic theoretical treatment of some of these processes and will be applied to various science topics such as the dissipation of acoustic gravity waves in the thermosphere and the subsequent effects of this wave dissipation on the mean state. Wave fluxes of sensible heat, momentum, and mass, and wave reflection in a non-isothermal atmosphere will be calculated, and tidal simulations will be produced using the equivalent gravity wave approach. An auxiliary model that sums over two species will be developed and used to assess multi-species effects in the full-wave model. Accounting for the presence of more than one species is necessary since wave dissipation due to collisions between species is an important heat source for the thermosphere.
Gravity waves that propagate through the thermosphere drive the gases out of static equilibrium and cause individual gases to oscillate with different amplitudes and phases while mutual diffusion attempts to mitigate these differences and restore diffusive equilibrium. The individual gases in the thermosphere may undergo wave motion and the amplitudes and phases of the waves exhibited by the individual gases relative to each other provide an important signature of wave periods, about which little is known in this region of the atmosphere. Wave effects are a complex function of composition, wave period and wavelength, as well as momentum and thermal collisional coupling, wave dissipation by eddy and molecular viscosity and thermal conduction, and reflection. A model that includes all these processes simultaneously is a fundamental requirement to furthering our understanding of gravity wave propagation, dissipation, and the wave characteristics in the thermosphere and to quantify poorly understood wave forcing of the thermosphere associated with lower atmospheric sources. Published satellite observations will be analyzed using the detailed model to test the model and to infer wave periods. The project addresses the goal of quantifying variations in and coupling between regions of the upper atmosphere. It also addresses fundamental diffusion processes in wave properties. The research will impact the field of upper atmospheric science by contributing substantially to wave processes currently not included in global general circulation models. It is planned to provide the new model to the community to help promote discovery and understanding. A full time graduate student will be involved in the research as well as a half-time undergraduate student.
